Compute postage only when required
fix tests
time series post Aggregation improved

move post aggregation to finalise results
Merge branch 'master' into optimize-postAgg-calculation

Conflicts:
	server/src/test/java/io/druid/client/CachingClusteredClientTest.java
fix casing and add comment
fix dependent PostAggregators
review comments
complete javadoc, add comment, use Lists.reverse
Add testOutOfOrderPruneDependentPostAgg
Merge pull request #467 from metamx/optimize-postAgg-calculation

Optimize post agg calculation